Alkylation of benzene



United States Patent 3,392,206 ALKYLATION 0F BENZENE Daniel J. Hurley,Oakmont, Robert W. Rosenthal, P ttsburgh, aud Roger 'C. Williamson,Gibsonia, Pa., ass gnors to Gulf Research & Development Company,Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Feb. 20,1964, Ser. No. 346,098 8 Claims. (Cl. 26067 1) This invention relates toa process for alkylating benzene with a mixture of normal alkylmonochlorides in the presence of a Lewis-type alkylation catalyst.

The mixture of normal alkyl monochlorides employed herein is obtained,for example, by chlorinating a mixture of normal parafiins havln-g fromsix to 20 carbon atoms, preferably having from 10 to carbon atoms, bypassing chlorine therethrough in the presence of a light source, such asactinic light, at a temperature of about to about 150 C. and a pressureof about 0 to about 10 pounds per square inch gauge. The normalparafiins employed can be obtained in any suitable manner, butpreferably are obtained by treating a kerosene in known manner with ureato form an adduct therewith. The adduct is thereafter decomposed and thedesired mixture of nor- "mal paraffins can thereby be obtained.Alternatively, the

normal paraffin mixture can be obtained by treating a kerosene in knownmanner using molecular sieves to separate the same'therefrom. In orderto obtain essentially only normal alkyl monochlorides, primary as wellas secondary, and avoid the formation of appreciable amounts of normalalkyl polychlorides, chlorination of said normal parafiins is terminatedwhen about 20 to about 30 percent, preferably about percent, of theavailable normal paraflins have a hydrogen thereon replaced withchlorine. The mixture obtained, therefore, comprises essentially fromabout 70 to about 80 percent by weight of unreacted normal parafiins andfrom about 20 to about percent by weight of primary and secondary normalalkyl monochlorides.

Following this, desirably benzene is reacted with only the normal alkylmonochlorides so produced in the presence of a Lewis-type alkylationcatalyst to obtain the desired monoalkyl benzene. The amount of catalystemployed can be, for example, from about one to about 15 percent byweight or higher, preferably from about 2.5 to about six percent byweight, based on the monochlorides present in the original charge. Whileit would be possible to separate a single carbon number normal paraffinfrom the same carbon number normal alkyl monochloride, by distillation,for example, it is almost impossible by distillation to separate anumber of normal paraflins from a mixture containing the same and anumber of normal alkyl monochlorides, since a normal alkyl monochloridewill distill at about the same temperature as a normal paraffin having ahigher number of carbon atoms. Since the normal parafiins will bevirtually unaffected under the alkylation conditions employed, the totalmixture of normal paratfins and normal alkyl monochlorides are broughtinto contact with benzene in the presence of the alkylation catalyst toobtain the desired alkylate. In order to drive the reaction in thedesired direction, a molar ratio of about three to about 20 mols ofbenzene, preferably about five to about eight mols, of benzene, per molof normal alkyl monochloride is employed. Thus the reaction mixture atthe beginning of the reaction contains a large amount of benzene, a

large amount of normal parafiins, a relatively small- T amount of normalalkyl chlorides and the alkylation catalyst.

The mixture described is then subjected to a temperature of about 20 toabout 80 C., preferably about 40 to about C., and a pressure of about 0to about ice 10 pounds per square inch, preferably about 0 to about 5pounds per square inch gauge, and as a result thereof benzene reactswith the normal alkyl monochlorides to form the desired alkylate andgaseous hydrogen chloride, which is permitted to escape from thereaction zone. Upon termination of the reaction, the alkylation catalystis permitted to settle in the reaction zone and the supernatantliquid ispassed to a distillation zone wherein unreacted benzene, normalparafiins and alkylate are separately recovered therefrom.

The alkylate obtained can be employed in many subsequent reactions andtherefore it is critical that it be substantially free of impurity whichmay create difiiculties in such reactions. An impurity which can easilyfind its way into the alkylate are unreacted normal alkyl monochlorides.This is so because it is diflicult or virtually impossible to separatethe same by distillation from admixture with alkylate havingapproximately the same number of carbon atoms. Thus, for example, wherethe alkylate so produced has from 10 to 15 carbon atoms and the same isto be reacted with sulfuric acid for the purpose of preparing adetergent therefrom, the presence of more than about 200 parts permillion, especially more than 300 parts per million of bound chlorine,therein is particularly bad, since the product acts as a skin irritantand is corrosive. Accordingly, since there is no easy method commonlyavailable to remove a number of unreacted normal alkyl monochloridesfrom the reaction mixture described above, and since it was thought thatno detrimental results would flow therefrom, it has been the custom tocontinue the alkylation reaction for an exceedingly long period of time,far beyond the point wherein it was believed alkylation ceased, so thatthere would be assurance of the virtual disappearance of theobjectionable normal alkyl monochlorides from the reaction mixture.

We have found, however, that it is critical in the defined alkylationreaction that the same be terminated within about five minutes, and inany event within about 15 minutes, of the time that the bound chlorinecontent of the alkylation reaction mixture is less than about 300 partsper million based on the alkyl benzene, preferably at the time the boundchlorine content thereof is less than about 200 parts per million. Wehave found that if the alkylation reaction is permitted to continuebeyond the point wherein all of the normal alkyl monochlorides havedisappeared, by reaction with benzene, the alkyl benzenes so obtainedwill begin to decompose and benzene and the corresponding alkanes, ornormal paraffins, will be produced.

This phenomenon, in the present context, was not easily apparent. Asnoted the reaction mixture contains a large amount of benzene and alarge amount of normal paraffins, and only a small portion thereof ismade up of normal alkyl monochlorides and/or the desired andcorresponding alkyl benzene product. Therefore, when the reaction waspermitted to go beyond the point wherein virtually all of the alkylmonochlorides had disappeared, the benzene and normal paraffinsresulting from decomposition 'of alkyl benzene were similar to thematerials already present in relatively large amounts therein and weretherefore almost impossible to detect.

In our work wherein we set out to determine whether or not detrimentalresults would be obtained when the alkylation reaction was permitted tocontinue for appreciably long periods of time beyond the point where allof the alkyl monochloride had disappeared, we employed in the reactiononly benzene and a single alkyl monochloride and found, unexpectedly,that upon disappearance of the alkyl monochloride progressively largeramount of alkane, or normal paraflin, corresponding to the alkylmonochloride employed 'wa's'foun'd as the reaction was permitted tocontinue. The amount of benzene was increased in an amount proportionalto the amount of alkane obtained. Since there was no alkane present inthe original mixture, we concluded that the alkane present and theadditional amount of benzene found in the reaction mixture was due todecomposition of alkyl benzene.

The invention can further be illustrated by the following.

Example I Into a flask there were placed 92 grams of benzene, 2.1 gramsof aluminum chloride and 100 grams of normal heptane. The normal heptanewas added for the purpose of providing an internal standard for gaschromatographic analysis. The mixture was raised to a temperature ofabout 34 to 35 C. and thereafter maintained at such temperature andatmospheric pressure for the remainder of the run. Over a period ofabout one minute there was added to the mixture defined above, while thesame was stirred, 30 grams of l-chlorododecane. On the basis of thenormal alkyl monochloride present, the amount of aluminum chloridepresent was seven percent by weight. Periodically during the reactiontwo grams of reaction product was removed from the reaction mixture andanalyzed by gas chromatography for its alkyl chloride content and forthe amount of normal dodecane present. Since dodecyl benzene producedwill decompose to equal molar amounts of benzene and dodecane, it wasthus possible to determine the amount of dodecyl benzene that wasdecomposed. The results are tabulated below in Table I.

TABLE I Time From Start M01 Percent M01 Percent Of Reaction, Monohalideof Alkyl Benminutes Present zone Deeomposed 2. None None 0. 97 None 3.63 None 5. 68 None 8. 79

Example II Example I was repeated, except that the temperature wasmaintained at about 39 to 40 C. The results are tabulated below in TableII.

TABLE II Time From Start Mol Percent M01 Percent Of Reaction, Monohalideof Alkyl Benminutes Present zone Decomposed None 0. 61

None 3.10

None 5. 68

None 7. 99

None 9.15

None 9. 80

Example III Example II was repeated, except that the amount of catalystused was five percent. The results obtained are tatbulated below inTable III.

TABLE III Time From Start Moi Percent Mol Percent Of Reaction,Monohalide of Alkyl Benminutes Present Zeno Decomposed None 0. 48

None 0.96

None 1. 92

None 3. 39

None 4. 55

None 5. 47

4 Example IV Example I was repeated, except that the temperature wasmaintained at about 27 to 28 C. The results obtained are tabulated belowin Table IV.

I Not taken.

Example I was repeated, but this time the catalyst concentration wasthree percent and the temperature was maintained at about 76 C. Theresults obtained are tabulated below in Table V.

TABLE V Time From Start Mol Percent Mol Percent of Reaction, Monohalideof Alkyl Benminutes Present zene Decomposed None 1. 30 None 8. 00

As pointed out above, the system employed in each of Examples 1, II,III, IV and V is not identical to the system employed in the processdescribed and defined herein. In the examples only reactants, benzeneand a single specific normal primary alkyl monochloride, and thealkylation catalyst were employed, whereas in the defined process alarge amount of normal secondary alkyl monochloride and some alkylpolychlorides are also present. The above examples are presented hereinmerely to emphasize and point out the inventive features of the presentprocess. Since no alkyl polychlorides are present, the reactionsdescribed in the examples will go at a faster rate than the claimedreaction. Accordingly in the claimed reaction, the conditions requiredfor the virtual disappearance, as described, of the normal alkylmonochlorides from the reaction mixture will include a temperature ofabout 20 to about 80 C., preferably about 40 to about 60 C., a pressureof about 0 to about 10 pounds per square inch gauge, preferably about 0to about 5 pounds per square inch gauge, and a reaction time of about 15to about 45 minutes, preferably about 20 to about 40 minutes. In anyevent, the data presented in the tables amply show that as the reactionis permitted to proceed beyond the point wherein all of the normal alkylmonochlorides have disappeared, progressively larger amounts of alkylbenzene is decomposed to unde sirable products. The data further showthat with increased temperature and/or increased catalyst concentration,not only does the desired alkylation reaction proceed more quickly toits conclusion, but the amount of decomposition products also increaseswhen the alkylation reaction is not terminated properly.

The alkylation reaction can be quickly terminated at the designated timeby turning off the stirrer, permitting the sludge (spent catalyst) tosettle and thereafer separating the reaction mixture therefrom. Anothermethod for terminating the reaction involves dumping the total reactionmixture into cold water, permitting the sludge to react with the waterand thereafter separating the organic layer, containing the desiredproduct, from the aqueous layer.

The determination as to when the reaction is to be terminated can bemade easily. Chromatographic analysis, for its alkyl chloride content,can be made of the reaction product obtained from a process identical toa proposed process. On the basis of the results obtained, the proposedprocess can be programed so that it can be terminated at the desiredtime to assure that no appreciable decomposition of alkyl benzene willresult. Alternatively, during the process the same can be monitored 5and the product analyzed for its alkyl chloride content by periodicallypulling a sample and analyzing the same by gas chromatography, usingeither a thermal conductivity detector or preferably an electron capturedetector which only shows organic halides.

The process described and defined herein can further be illustrated bythe following. Into a reactor equipped with a stirrer there wereintroduced 113 grams of benzene and 1.14 grams of aluminum chloride. Thetemperature of this mixture was raised to 63.5 C. and the same wasmaintained at this temperature level and at atmospheric pressurethroughout the run. Over a period of one minute 200 grams of thefollowing mixture was added to the reaction zone: 78 percent by weightof normal paraflins having from 10 to 15 carbon atoms, 0.6 percent byweight of C normal alkyl monochlorides, 4.6 percent by weight of Cnormal alkyl monochlorides, 4.8 percent by weight of C normal alkylmonochlorides, 5.1 percent by weight of C normal alkyl monochlorides,3.4 percent by weight of C normal alkyl monochlorides, and 0.3 percentby weight of C normal alkyl monochlorides. Periodically during thereaction samples were withdrawn from the reaction mixture and analyzedby gravimetric analysis for their bound chlorine content and by gaschromatography for the mol percent of alkyl benzene decomposed. Theresults obtained are tabulated below in Table VI. On the basis 'of theresults obtained, a process is programed employing the reactionconditions described in this example wherein the reaction is terminatedpromptly upon the virtual disappearance of the normal alkylmonochlorides, from the reaction product.

TABLE VI Time From Start Of Bound Chlorine, Mol Percent of Reaction,minutes Parts per Million Alkyl Benzene Deeomposed Obviously, manymodifications and variations of the invention, as hereinabove set forth,can be made without departing from the spirit and scope thereof, andtherefore only such limitations should be imposed as are indicated inthe appended claims.

We claim:

1. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventing appreciable decomposition of the alkyl benzene which isformed to benzene and the corresponding alkanes which comprisessubjecting to alkylation conditions in the presence of a Lewis-typealkylation catalyst a mixture consisting essentially of benzene, normalparaifin selected from the group having from six to 20 carbon atoms,normal alkyl monochlorides selected from the group having from six to 20carbon atoms, wherein the molar ratio of benzene to said normal alkylmonochlorides is from about three to about 20 and the weight ratio ofsaid parafiins to said normal alkyl monochlorides is from about 70 toabout 80 percent of the former to about 20 to about 30 percent of thelatter, passing the hydrogen chloride formed out at the reaction zone,determining when the bound chlorine content of the reaction mixturefalls to less than about 300 parts per million, and terminating thealkylation reaction in response to said chlorine determination toprevent appreciable decomposition of alkyl benzene.

2. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventing appreciable decomposition of the alkyl benzene which isformed to benzene and the corresponding alkanes which comprisessubjecting to alkylation conditions in the presence of a Lewis-typealkylation catalyst a mixture consisting essentially of benzene, normalparafiins selected from the group having from six to 20 carbon atoms,normal alkyl monochlorides selected from the group having from six to 20carbon atoms, wherein the molar ratio of benzene to said normal alkylmonochlorides is from about three to about 20 and the weight'ratio ofsaid paraffins to said normal alkyl monochlorides is from about 70 toabout percent of the former to about 20 to about 30percent of thelatter, passing the hydrogen chloride formed out of the reaction zone,determining when the bound chlorine content of the reaction mixturefalls to less than about 200 parts per million, and terminating thealkylation reaction in response to said chlorine determination toprevent appreciabledecomposition of alkyl benzene;

3. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventing appreciable decomposition of the alkyl benzene which isformed to benzene and the corresponding alkanes which comprisessubjecting to alkylation conditions in the presence of an aluminumchloride alkylation catalyst a mixture consisting essentially ofbenzene, normal parafiins selected from the group having from six to 20carbon atoms, normal alkyl monochlorides selected from the group havingfrom six to 20 carbon atoms, wherein the molar ratio of benzene to saidnormal alkyl monochlorides is from about three to about 20 and theweight ratio of saidparaffins to said normal alkyl monochlorides is fromabout 70 to about 80 percent of the former to about 20to about 30percent of the latter, passing the hydrogen chloride formed out of'thereaction zone, determining when the bound chlorine content of thereaction mixture falls to less than about 300 parts per million, andterminating the alkylation reaction in response to said chlorinedetermination to prevent appreciable decomposition of alkyl benzene.

4. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventing appreciable decomposition of thealkyl benzene which is formedto benzene and the corresponding alkanes which comprises subjecting toalkylation conditions in the presence of an aluminum chloride alkylationcatalyst a mixture consisting essentially of benzene, normal parafiinsselected from the group having from six to 20 carbon atoms, normal alkylmonochlorides selected from the group having from six to 20 carbonatoms, wherein the molar ratio of benzene to said normal alkylmonochlorides is from about three to apout 20 and the weight ratio ofsaid parafiins to said normal alkyl monochlorides is from about 70 toabout 80 percent of the former to about 20 to about 30 percent of thelatter, passing the hydrogen chloride formed out of the reaction zone,determining when the bound chlorine content of the reaction mixturefalls to less than about 200 parts per million and terminating thealkylation reaction in response to said chlorine determination toprevent appreciable decomposition of alkyl benzene.

5. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventingappreciable decomposition of the alkyl benzene which is formedto benzene and the corresponding alkanes which comprises subjecting toalkylation conditions in the presence of an aluminum chloride alkylationcatalyst a mixture consisting essentially of benzene, normal paraflinsselected from the group having from 10 to 15 carbon atoms, normal alkylmonochlorides selected from the group having from 10 to 15 carbon atoms,wherein the molar ratio of benzene to said normal alkyl monochlorides isfrom about three to about 20 and the weight ratio of said paraflins tosaid normal alkyl monochlorides is from about 70 to about 80 percent ofthe former to about 20 to about 30 percent of the latter, passing thehydrogen chloride formed out of the reaction zone, determining when thebound chlorine content of the reaction mixture falls to less than about300 parts per million, and terminating the alkylation reaction inresponse to said chlorine determination to prevent appreciabledecomposition of alkyl benzene.

6. A process for alkylating benzene with a number of normal alkylmonochlorides at a temperature between about 20 and 80 C. whilepreventing appreciable decomposition of the alkyl benzene which isformed to hen zene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of an aluminum chloridealkylation catalyst a mixture consisting essentially of benzene, normalparafiins selected from the group having from 10 to carbon atoms, normalalkyl monochlorides selected from the group having from 10 to 15 carbonatoms, wherein the molar ratio of benzene to said normal alkylmonochlorides is from about three to about and the weight ratio of saidparafiins to said normal alkyl monochlorides is from about 70 to about80 percent of the former to about 20 to about 30 percent of the latter,passing the hydrogen chloride formed out of the reaction zone,determining when the bound chlorine content of the reaction mixturefalls to less than about 200 parts per million, and terminating thealkylation reaction in response to said chlorine determination toprevent appreciable decomposition of alkyl benzene.

7. A process for alkylating benzene with a number of normal alkylmonochlorides while preventing appreciable decomposition of the alkylbenzene which is formed to benzene and the corresponding alkanes whichcomprises subjecting to a temperature of about 20 to about 80 C. in thepresence of from about one to about 15 percent by weight of an aluminumchloride alkylation catalyst a mixture consisting essentially ofbenzene, normal parafiins selected from the group having from 10 to 15carbon atoms, normal alkyl monochlorides selected from the group havingfrom 10 to 15 carbon atoms, wherein the molar ratio of benzene to saidnormal alkyl monochlorides is from about three to about 20 and theweight ratio of said parafiins to said normal alkyl monochlorides isfrom about 70 to about 80 percent of the former to about 20 to about 30percent of the latter, passing the hydrogen chloride formed out of thereaction zone, determining when the bound chlorine content of thereaction mixture falls to less than about 300 parts per million, andterminating the alkylation reaction in response to said chlorinedetermination to prevent appreciable decomposition of alkyl benzene.

8. A process for alkylating benzene with a number of normal alkylmonochlorides while preventing appreciable decomposition of the alkylbenzene which is formed to benzene and the corresponding alkanes whichcomprises subjecting to a temperature of about 20 to about 80 C. in thepresence of from about one to about 15 percent by weight of an aluminumchloride alkylation catalyst a mixture consisting essentially ofbenzene, normal paraffins selected from the group having from 10 to 15carbon atoms, normal alkyl monochlorides selected from the group havingfrom 10 to 15 carbon atoms, wherein the molar ratio of benzene to saidnormal alkyl monochlorides is from about three to about 20 and theweight ratio of said paratfins to said normal alkyl monochlorides isfrom about to about percent of the former to about 20 to about 30percent of the latter, passing the hydrogen chloride formed out of thereaction zone, determining when the bound chlorine content of thereaction mixture falls to less than about 200 parts per million, andtermimating the alkylation reaction in response to said chlorinedetermination to prevent appreciable decomposition of alkyl benzene.

References Cited UNITED STATES PATENTS 1,337,317 4/ 1920 Houlehan260-672 2,072,061 2/1937 Thomas 260-671 3,235,616 2/1966 Sharman 260-6721,995,827 3/1935 Thomas 260-671 OTHER REFERENCES Thomas, AnhydrousAluminum Chloride in Organic Chemistry, Reinhold Publishing Corp., NewYork (1941), pp. 78 and 79 relied upon.

DELBERT E. GANTZ, Primary Examiner.

CURTIS R. DAVIS, Assistant Examiner.

1. A PROCESS FOR ALKYLATING BENZENE WITH A NUMBER OF NORMAL ALKYLMONOCHLORIDES AT A TEMPERATURE BETWEEN ABOUT 20* AND 80*C. WHILEPREVENTING APPRECIABLE DECOMPOSITION OF THE ALKYL BENZENE WHICH ISFORMED TO BENZENE AND THE CORRESPONDING ALKANES WHICH COMPRISESSUBJECTING TO ALKYLATION CONDITIONS IN THE PRESENCE OF A LEWIS-TYPEALKYLATION CATALYST A MIXTURE CONSISTING ESSENTIALLY OF BENZENE, NORMALPARAFFIN SELECTED FROM THE GROUP HAVING FROM SIX TO 20 CARBON ATOMS,NORMAL ALKYL MONOCHLORIDES SELECTED FROM THE GROUP HAVING FROM SIX TO 20CARBON ATOMS, WHEREIN THE MOLAR RATIO OF BENZENE TO SAID NORMAL ALKYLMONOCHLORIDES IS FROM ABOUT THREE TO ABOUT 20 AND THE WEIGHT RATIO OFSAID PARAFFINS TO SAID NORMAL ALKYL MONOCHLORIDES IS FROM ABOUT 70 TOABOUT 80 PERCENT OF THE FORMER TO ABOUT 20 TO ABOUT 30 PERCENT OF THELATTER, PASSING THE HYDROGEN CHLORIDE FORMED OUT AT THE REACTION ZONE,DETERMINING WHEN THE BOUND CHLORINE CONTENT OF THE REACTION MIXTUREFALLS TO LESS THAN ABOUT 300 PARTS PER MILLION, AND TERMINATING THEALKYLATION REACTION IN RESPONSE TO SAID CHLORINE DETERMINATION TOPREVENT APPRECIABLE DECOMPOSITION OF ALKYL BENZENE.